X-ray generating device



1940. J. w. M. DU MOND 2.2o9,963

` X-RAY GENERATING DEVICE Filed June 18, 1938 4 Sheets-Sheet l ATTORNEY Aug. 76, 1940. J. w. M. DU MOND X-RAY GENERATING DEYICE ;Filed June 18, 1938 4 Sheets-Sheet 2 INVENTOR.

%RNEYS Aug. 6, 1940. J. w. M. DU MOND X-RAY GENERATING DEVICE Filed June 18, 1958 4 Sheets-Sheet 3 20" V 75535 14. M. DU/VO/v,

INVENTOR. BY M %61. ATTORNEY Aug. 6, l940. J. w. M. DU MOND X- RAY GENERATING DEVICE Filed June 18, 1938 4`Sh'eets-Sheet 4 %555 V/ 7 &Mwa/va, INVENTOR. BY m( ATTORNEYS Patented Aug. 6, 1940 UNITED' STATES z re::

PATENT OFFICE X-RAY GENERATIN G DEVICE Application June 18, 1938, Serial No. 214,483

17 Claims.

This invention relates to X-ray tube Constructions, and pertains more particularly to X-ray tube constructions in which continuous relative movement is obtained between the target surface and the focal spot of the electron beam from the cathode.

One of the particular objects of the present invention is to provide an X-ray tube adapte-d for operation under very high power input conditions, over extended periocls, without detriment.

A further object of the invention is to provide an X-ray tube employing a foeal spot of smaller projccted size than has been hitherto possible in r high power X-ray tubes, whereby radiographs of greater definition are obtained, due to a reduction in the geometrical unsharpness of the radiographic images formed by the tube.

A further object of the invention is to provide an X-ray tube structure in which the emission of X-rays from the target is obtained in a direction such as to utilize the maximum quantity of generated X-rays in radiography.

A further object of the invention is to provide a movable anode X-ray tube which is completely shielded internally against the escape of unwanted X-rays.

A further object is to provide a tube construction in which the relatively movable parts are mounted in hearing means located externally of the exhausted area, wherefore hearing troubles may be reduced to an absolute minimum. A further object of the invention is toprovide a movable anode X-ray tube Construction which is of shock-proof design.

A further object of the invention is to provide a rotatable X-ray tube Construction mounted within an enclosed housing on hearing means disposed wholly outside the evacuate d structure, such enclosed housing being adapted to contain a body of fluid of high dielectric strength which Will serve as an insulating medium, a cooling medium, and as a lubricating agent for the bearing means.

A further object is to provide a structurecharacterized by a complete freedom from Vibration due to unbalanced rotatng parts.

A further object of the invention is to provide an X-ray tube construction embodying a rotat- 50 ing target member in which positive and continuous circulatien of cooling fluid is provided adjacent all pcrtions of the Construction which are subjected to heating, wherefore the Operating temperature of the device may be kept at an advantageously low value under materiallygreater power input values than have hitherto been obt ained.

A further object of the invention is to provide an X-ray tube Construction having a rotatable anode member-provided with a target surface portion of e-xtended area located at points radially removed from the axis of rotation of said anode member and movable therewith in a fixed annular path, together with a cathode structure adapted to generate an electron beam of small cross-sectional area which is directed into impingement upon the target surface portion from one side of said path of rotation as a small "focal" spot, resulting in the production of X-rays directed away from the point of such impingement at the other side of the path of rotation. The electron impingement in the small "focal spot" on the rotating target portion of the anode results in a scanning" of the entire target surface portion, and, inasmuch as the focal spot" remains substantially fixed in Space and the target surface portion rotates in its fixed annular path under impingement by the cathode beam, this scanning by the focal spot results in a distribution of the heating efiect of the electron stream upon a relatively extended area of the target while restricting the projected area of the focal spot (which affects the geomctrical sharpness of the structure for ra diography) to a minimum. v

The previously suggested forms of moving anode X-ray tub-es have, in general, provided an anode Construction comprising a large mass of metal capable' of absorbing a relatively large quantity of heat, and have relied upon a short enough exposure to the electron beam so that any one portion of the target surface will not be allowed to reach a dangerous Operating temperature. This form of device has relied upon bearing members disposed wholly within the evacuated space, and it has been found that the useful life of these particular tubes is unpredictable; It will be appreciated that if the bearings should stick, and the electron beam 'be allowed to impinge upon the target for any significant length of time, the allowable Operating temperature i will be excee ded almost instantaneously and serious damage to the equipment will result. An additional defect has resulted from the difiiculty of cooling the target member at a sufficiently rapid rate to permit the device tobe used for any protracted period. The conventional cooling arrangement provided is that of telescoping heat-exchange devices which depend upon loss of heat from the target member by radiation into a fixed member which may be subjected to water cooling. The problem of causing any quantity of heat to be transmitted across the evacuated space, at the small temperature differences which are experienced, is apparent.

several features are now felt to be needed in commercial radiography, both of human bodies and for the examination of massive castings, and the like. Among these requirements may be enumerated:

(a) The provision of a smaller focal spot (to decrease the geometrical unsharpness of the images formed by the X-rays):

The provision of sufficient intensity of radiation as to make possible short exposure times Compared to the movement of body organs, that is, to take care of movements on the order of centimeters per second;

(c) The provision of a moving anode structure which Will allow the target to move its surface over a distance many times the diameter of the focal spot during the time of exposure;

(d) The focal spot must be stationary in space (relative to objects in the room), especially as regards motions that would blur the radiographic image;

(e) Increased high long-time average heat dissipation capacity from the target, whereby sustained high input energies may be secured;

(f) Low first cost and long life.

The above features are secured according to the present invention by provision of a rotatable anode structure carrying a target face of extended area formed as a surface of revolution, removed from. the axis of rotation of said anode, and adapted to be moved in an annular path, together with means for generating and directing an electron stream into impingement with the target face at a position substantially fixed in space and wholly from one side of said path, resulting in the production of X-rays directed away from said target face at the other side of said path.

Other features and objects of the invention Will be brought out in the ensuing description of certain preferr ed embodiments, or will be apparent therefrom. Referring to the accompanying drawings:

Fig. 1 is a longitudinal vertical section of one form of the present X-ray tube, showing the use of a cylindrical target member, the cathode member being so estab lished as to direct the cathode beam against the interior surface of the anode member and at an angle to the axis of rotation of said member;

Fig. 2 is a transverse section thereof taken on line 2-2 in Fig. 1;

Fig. 3 is a transverse detail thereof taken on line 3-3 in Fig. 1;

Fig. 4 is a detail sectional View of a' portion thereof, taken on line 4-4 in Fig. 1;

Fig. 5 is a View corresponding to Fig. 1, showing a further modification of the invention in which the anode member is of conical configuration and the cathode member is mounted for ,rotation about an axis extending parallel to, but

offset with respect to, the axis of rotation of the anode member;

Fig. 6 is a partly broken-away longitudinal section, corresponding to that shown in Fig. 1, illustrating a modified form of Construction in which the conical anode and the cathode supporting structures are mounted for rotation upon a common axis, and means are provided for defiectng the electron beam into im'pingement against the internal surface of the anode member;

Fig. 7 is a transverse section taken on line 'I-'I in Fig. 6;

Figs. 8 and 9 are fragmentary views corresponding to' the left-hand end of Figs. 1, 5, or 6, showing further modifications of an X-ray tube structure according to the present invention;

and

Figs. 10, 11, and 12 illustrate the classical theoretical law of X-ray (continuous spectrum) emission at low, medium, and high Voltages, respectively, for electrons decelerated along their original direction of motion.

Referring to Figs. 1 through 4:, one embodiment of the invention is illustrated as comprising a housing provided with a removable cover member 2 secured to the housing I in any suitable manner as through the agency of screws 3, a fluid-tight joint being preferably provided as through the agency of a gasket member 4. The X-ray tube Construction comprising a rotatable anode member 5 and a rotatable cathode assembly B, which in this instance are joined by a fiexible gas-tight tube nember l such as a "Sylphon" bellows, is mounted on a framework 8 which is independent of housing and is preferably mounted upon the cover 2 as at a plurality of spaced points 9. This Construction provides for removal of the X-ray tube assembly from the body of the housing for inspection or repair, the electrical connection to the cathode member being provided with male and female contact elements as more particularly described hereinafter.

The X-ray tube proper is defined by the anode member 5, which is of generally conical or cylindrical Construction and includes a thin window or diaphragm secured at the outer end thereof, the flexible tube member 'I and the cathode assembly 6, which includes a hub member !2 carrying the cathode stem !3 provided with a filament !4 at its inner end, the stern !3 being suitably insulated from the hub !2 as through a glass seal !5. The necessary electrical connection to the filament !4 may be provided by making the stem !3 of tubular Construction and providing a central conductor !6 extending along the length of the stern !3 and insulated therefrom. The stem !3 and conductor !6 may be connected to the filament supply energy through the agency of contact rings !1 and !B secured to the stem !3 and conductor !6 and engaged by suitable contact fingers such as are shown at !9 in Fig. 3, which are electrically connected to conductor rings 2!! mounted in an insulating support 2! terminating in a plug Connector 22 adapted to mate with a connecting socket 23 mounted .on the housing and suitably associated with a high tension lead-in cable 24. A vacuum seal may be provided between the tube !3 and the member !6 according to conventional practice, asby providing thin metal diaphragm members 25 hermetically sealed to the respective members !3 and !6 and hermetically joined as by means of a glass sealing ring 26, this construction being more particularly illustrated in detail in Fig. 4.

The anode member 5 is mounted for rotation in the housing as through the agency of a hearing member 26 mounted on a support frame 21 which is secured to the framework 8. The hub member !2 of the cathode assembly is similarly mounted in bearing means 28 carried by a supporting ring 29 mounted on a rearwardly projecting portion of the interior framework. The conductor rings 20 and the connector'member 2| may be carried on the rearward projection 30 of the frame assembly, as is more particularly illustratecl in Fig. 3, such portion being preferably formed of non-conductive material such as "Bakelite" suitable means are provided for eecting rotation of the X-ray tube Construction, as by pro-.

viding a gear member 3l located on a ange portion 32 of the anode member 5, engaged by a driving gear 33 carried on a shaft 34 and driven by a suitable motor 35, which may be located exteriorly of the housing l. v

According to this Construction, the cathode assembly is mounted for rotation about the axis which intersects the axis of rotation of the anode member 5, in position to direct the cathode beam CB upon the inner wall 36 of the hollow anode, and the resulting X-rays X-R will be directed outwardly through the window H, another win-` dow being provided in the` cover 2 as at 38 to facilitate the transmission of a useful portion of such X-rays.

The provision of the b'earing means 26 and 28 wholly exteriorly of the evacuated envelope, and the dispositio-n of the rotating assembly within the housing l provide for continuo us lubrication of such bearing means by the submerging fluid contained within the housing. This fluid is relied upon for 1) insulation of the high-' tension portions of the device from. the housing, which is grounded, (2) lubrication of the bearing means, and (3) cooling of the X-ray tube and particularly the anode portion thereof. suitable inlet and outlet connectionsmay be provided, as at 95 and 91, if desired, for continuous supply and withdrawal of the submer-ging fluid, in association with an external heat-exchange or cooler device, although in general sufcient cooling of the fluid body is obtained by direct radiameans of bearings 45, and a second supporting Construction is provided as at 46 on a rearwardly extending portion of the support 44, carrying the cathode assembly 41 through the' agency of bearings 48. A further extension of the supporting Construction may be provided as at 49, preferably of insulating'material, such as Bakelite," for example, on which is mounted a Connector ring assembly such as that shown at H through 20 in connection with Fig. 1. This portion of the device may terminate in a male plug connecter corresponding to the member 22 above, and provided with spring contact members 5l which are adapted to engage with a suitable female Connector which may be mounted on the housing 42 in accordance with the teaching in connection with the first 'form of the invention.

The anode member 4! is shown as having a conical internal face 52 having portions lying' along the projection of the axis of the cathode member 40 in position to receive the cathode beam therefrom, as indicated at 032.' A suitable window member is provided as at 53 across the forward end` of the anode member,- through which the X rays are projected, as at X-Rz and a correspondingly positioned window 54 is provided in the cover 53. A flexible tube Connector will be provided between the anode 4! and the cathode hub 41, as at 55, corresponding to the fiexible tube 'l shown in the first form of the device, and suitable driving means for the rotatable tube assembly will also be provided, as through the agency of gear members 55 and 55, the latter mounted on the shaft 57 as in the firste described form of the invention.

The form of device shown in Figs. 6 and '7 may comprise a housing 58 provided with a cover member 59 carrying a support 55 on which the anode member si is mounted for rotation as through the agency of bearings 52, the anode member being suitably driven through the agency of gears 53 and 64 and shaft 55. The cathode member '55 is disposed for coaxial rotation with the anode El, and the electron beam CB3 result I ing therefrom is defiected into engagement with the target surface BT of the anode Gi through lustrated the use of electromagnets provided,

with external connecting leads 59 and interconnecting conductors H. The necessary connection of the filament supply current may be provided as at 12 through the agency of a con nector means of the type shown at ll through 20 in Figs. 1 to 4. suitable windows will be pro'- vided as at SI' and 59' at the end of the anode Bl and on the cover 59 respectively, for transmission of the generated X-rays X-Rs. The type of tube Construction illustrated i Fig. 8 is structurally comparable to that shown in Fig. 5, with the exception that the anode member 13 is made substantially cylindrical in shape and the inner substantially plane surface 'M' of the window 14 is employed in the role of target member, the cathode beam CB4 from the cathode 16 being directed parallel to the axis of rotation of the anode but displaced therefrom, as shown, so as to sweep out an annular path on the surface 14', or, alternatively, the cathode beam may be directed at an angle to such axis after the manner shown in the first form of the invention.

The form of the invention shown in Fig. 9 may V comprise a housing 8! provided with a removable cover member 82 carrying the anode-end bearing 83 and the corresponding cathode-end bearing '(not shown) through the agency of a.

suitable supporting frame 85, corresponding to the frame 8, above. The anode 35 is shown as a truncated cone-shaped member, mounted con centrically of the bearing 83 through the agency of an electrically-conductive X-ray-permeable window member 85 and an anode support mem# ber 8'! mounted on the hearing 83. A cathode is shown at 88, which may be mounted in a manner comparable to that shown and described in connection with Fig. 5, or alternatively and equivalently, after the manner of the cathode !3 in the first form of the invention. The cathode 88 is adapted to produce acathode beam CB5, which is directed into impingement with the inclined annular wall 85' of the anode, resulting in the generation of an X-ray beam X-R5 through the window member 86. The cover 82 is provided with a window member 82a in position to permit the passage of the beam X-Rs exteriorly of the housing Bl, as will be apparent to one skilled in the art.

The anode 85 is preferably hollowed out at its outer side, to form a recess 89, and the cooling fluid provided about the X-ray structure may be positively circulated into cooling contact with such anode, as by means of a gear pump mounted on the frame 34 and driven by the same member which effects rotation of the X-ray structure, such as a driven shaft carrying a gear 92 meshing with a gear portion 81' integral with the anode support member 81. The

intake supply line (not shown) for the pump 90 will preferably communicate with a lower portion of the housing I so as to insure a continuous supply of cooling fluid thereto, and the discharge line 93 for the pump 90 may be directed into the recess 89 adjacent the axis of rotation of the anode.

The cathode supporting structure will be hermetically joined to the anode support structure 81 through the agency of a fiexible tube 94, corresponding to the tube 'i in the first form of device and the balance of the tube structure, including the current supply connections, may be comparable to that shown in Fig. 5.

The target window ?4 in the form of structure illustrated in Fig. 8 may be cooled by a stream of cooling fluid, if desired, in a manner comparable to that employed in connection with Fig. 9, as through the agency of a gear pump 95 mounted on the hearing support framework and operatively associated with the driven shaft member provided for rotation of the anode assembly 13. The pump 35 may discharge through a passage 96 in the cover portion of the housing, at approximately the center of the window l l. The cover is preferably provided with an X-raypermeable window member 91 in position to transmit the X-ray beam X-RA.

Positive circulation of cooling fluid to any desired portion of the anode structure may be provided for the forms illustrated in Figs. l through 7, if desired, as will be apparent.

In Figs. 10, ll, and 12 I have illustrated, graphically, the classical theoretical angular distribution law of continuous spectrum X-ray emission resulting from electrons suddenly decelerated in the direction of their motion, as by impingment upon a thin target member, at various electron speeds obtained by the use of various voltages. These curves represent, respectively, the distribution pattern of X-rays produced by electrons at three different speeds, Fig. 10 illustrating that obtained at comparatively low voltages, that shown in Fig. 11 illustrating the pattern obtained at approximately 50,000 volts, and the curve in Fig. 12 illustrating the pattern obtained at approximately 500,000 volts. These curves are obtained from the classical theoretical formula:

the electron. In this equation, the expression [l-(1J`/C)cos9] is responsible for the forward tilting of the direction of maximum emission as the electron speed is increased.

The actual emission from X-ray targets actually deviates from this formula because the electrons are not all decelerated exactly in the direction of their original motion; this formula does, however, account for the increased forward intensity as the cathode rays (electrons) approach the velocity of light.

From these curves it may be seen that at high electron voltages the direction of maximum emission of the X-ray approaches more and more the original direction of the generating electron. Advantage is' taken of this physical fact in the X-ray tubes of the present invention, wherein the target surface to be mpinged by the electrons is caused to move in an annular path radially displaced from the axis of rotation of the anode member, and the electron beam is brought into impingement upon the target surface from one side of said annular path while the' utilized X-ray beam resulting from such impingement is' directed away from the target surface at the other side of said path and in the direction in which the maximum emission occurs. This feature makes it possible to cause the X-ray radiation to leave the X-ray tube construction at the end of the tube rather than at the side of the tube according to conventional Construction, and makes possible the provision of anode members which may constitute a portion of the X-ray tube envelope and which, consequently, may be directlyexposed to the cooling action of a fluid body. In each form of apparatus herein described, the anode member may be completely immersed in a body of fluid of high dielectric strength such as oil, contained within the housing structure, and this submergence, taken with the circulatory effects produced by the rapid rotation of the tube structure, results in the rapid dissipation of heat from the anode body i The form shown in Figs. 6 and '7 is more adapted to the production of X-rays at comparatively low electron velocities, while the form illustrated in Fig. 8 is adapted to utilize the maximum Voltage practicable in X-ray tubes, inasmuch as the X-ray beam resulting from the impingement of the cathode beam '15 may extend coaxially with such beam, if necessary, without absorption by shadowing portions of the anode body.

The forms illustrated in Figs. l, 5, and 9 are adapted for intermediate and fairly high electron voltages, and it will be appreciated that the form in Fig. 1 may be Varied with respect to the angle of intersection of the axis of the cathode and anode, by the employment of modified supporting structures as will be apparent to one skilled in the art, wherefore'the tube may be employed for substantially any desired range of electron voltages with maximum emciency.

The tube constructions of the present invention admit themselves to complete internal shielding against stray X-rays, as by coating the exterior, or, preferably, as by lining the interior of the housing with a lead sheath or the like, as indicated at 98 in Fig. 5, if desired. shield members opaque to X-rays may also be provided on the cathode stem, as indicated at 80 in Fig. 6, for example.

The electron beam is emitted from the cathode with a circular cross-section centered about the axis of rotation of the cathode member so that this rotation does not influence the shape or position of the focal spot. The oblique impingement of this beam on the anode surface gives an elongated, approximately elliptical, focal spot whose increased area on the target facilitates cooling. The oblique emergence of the utilized cone oi X-rays reduces the projected area of this focal spot so as to minimize geometrical unsharpness of the images formed by the X-rays, as in radiography. v

The target surface portions of the anodes employed in the present constructions may be of any desired metallic material, such as tungsten, gold, or the like, while the base portion of the anode is preferably formed of a metal having high heat conductivity, whereby the heat generated by the electron impingement will rapidly be carried away from the target surface. The target material may be formed as a layer on the anode body, as indicated at L in Figs 1, 5, 6, and 9. The thin targetemployed in the form shown in Fig. 8 may comprise a base of copper foil, provided with a thin layer of gold, for example, or may be formed as a thin sheet of a relatively hard gold-silver or A gold-copper alloy. Owing to the very rapid heat dissipation made possible by the present constructions, low melting-point target layers, such as of lead, may be effectively employed.

The target surface portions of the anode member are in each case removed from the X-raypermeable window member in a direction towards the opposite end of the evacuated envelope, and in each casethe origin of the cathode beam will be located at a point further removed in the same direction. The target surface portions will also in each case comprise a surface of revolution, of substantially conical configuration (it being appreciated that a cylinder, asin Fig. 1, is one limiting form of a cone, while a plane, as in Fig. 8, is the other limiting form of a cone).

The expression adapted for rotation about a line extending along the length thereof as employed in the claims in description of the manner in which the elongated evacuated housing is established for rotation, will be understood to include not only a straight line (as in the form shown in Fig. 6), but also a simple curved line (as in the form shown in Fig. 1), or a compound curved line (as in the forms shown in Figs. 5, 8, and 9). In each case this line about which the rotation is effected will be straight at the position of the anode and cathode members, due to the fixed rotative path of these members as defined by the bearing means, and such portions of such line may be used as reference lines to describe the position of the target surface portion, the direction 'of propagation of the electron beams, or the like. timum rate of rotation of the X-ray envelope for a given power input is primarily a thermal problem, the theoretical considerations and mathematical treatment of which, as applied to X-ray assemblies which provide a mobile focalspot (either by actual movement of the anode or by movement of the cathode) will be found in an article in the July 1935 issue of the Review c-f Scientific Instruments, published by the American Institute of Physics, of which I am coauthor.

In the form shown in Figs. 6 and 7 the electromagnets 68 constitute the means for directing the electron beam into impingement upon the target surface portion of the anode, While in the remaining forms reliance is placed upon a "focusing" type of cathode to project a directed beam Determination of the op-" of small cross-sectional area upon the anode The use of modified types of cathode structures will be apparent to one skilled in the art, having in mind the particular type of focal spot desired for a particular use of the apparatus. The focal spot'of the cathode beam, i. e., the area on the target member which is impinged by the cathode beam, will ineach case be substantially fixed' in space, to realize a low degree jof' geometrical unsharpness in the X-ray beams. This relative `xity in space depends, however, upon the fixity of the axes of rotation in space, and will be un-g derstood to contemplate the use of suitable supporting means adapted'to securethe entire X-ray generating, unit against movement during an exposure.

The electrical connections to the device, for application of high tension current tothe cathode and anode, may be established in any common' manner, as will be apparent to those skilled in the art. In the accompanying drawings the anode members of the several forms of device are shown as grounded (as through the bearing 26 and supportZ', or' through the gear 33) to the' housing (such as shown at i) which encloses the entire X-rayenvelope, and the high tension side of a current-supply transformer may be connected to either of the leads communicating With i the conductor rings 20, with the low tension side of such transformer being grounded to the housing. The 'lead connected with the other conductor ring 20 is Conveniently connected to one '1. An X-ray generating device which comprises: an evacuated envelope; a rotatable anode member defining a portion'of said envelope and provided with an internal target surface portionof extended area removed from the' axis of rotation of said anode member and movable therewith in a fixed annular path; means for `generating and directing an electron beam, ,from a source located within said envelope and at one side of said fixed path, against said target surface portion at a position on said path substantially fixed in space, to cause generation of X- rays directed away from said target surface .portion at the other side of said path; and external housing surrounding said evacuated envelope and adapted to contain a body of cooling fluid in contact with the exterior surface of such portions of said anode member as define a portion of said envelope, and means for' rotating said anode member to cause said target surface portion to pass through 'said position. i r

2. An X-ray generating device which comprises: 'an elongated evacuated envelope mounted for rotation about a line extending longitudinally thereof, and provided with an annular target surface portion disposed transversely with respect to said line adjacent one end of said envelope, said envelope including an X-raymoved from said target surface portion towards pingement upon a restricted area upon-said target surface portion at a position substantialy fixed in space, from a source located within said envelope and longitudinally removed from said target surface portion towards the other end of said envelope, to cause generation of X-rays directed away from said target surface portion and through said Window member; and means for rotating said envelope to cause said target surface portion to rotate through said position.

3. The X-ray generating device set forth in claim 2, and comprising in addition an external housing surrounding said evacuated envelope and adapted to contain a body of cooling fluid in contact therewith.

4. An X-ray generating device which comprises: an elongated evacuated envelope mounted for rotation about a line extending along the length thereof and provided with an anode member having a target portion of extended area adjacent one end of said envelope, said target portion comprising a surface of revolution and having an aXis of rotation lying along said line adjacent said one end and being symmetrical with respect to but radially removed from said axis; means for generating and directing an electron beam towards said one end into impingement upon a restricted area on said target portion, at a position substantially fixed in space, from a source located within said envelope and spaced from said target portion in a direction toward the other end of said envelope, to cause generation of X-rays directed away from said target portion toward said one end` of said envelope; and means for rotating said envelope and said anode member to cause said target portion to rotate through said position and thus eect relative movement of? said restricted area of electron impingement over the extended area, of said target surface portion. V

5. An .X-ray generating device which comprises: an elongated evacuated envelope mounted for rotation about a line extending along the length thereof, and provided with an X-raypermeable window member at one end; a conical anode member rotatable with and forming a part of said envelope, symmetrically disposed with respect to said line at one end of said envelope and located inwardly of said window member adjacent said one end; means for generating and c'lirecting an electron beam towards said one end into impingement upon said conical anode, at a position substantially fixed in space, from a source located within said envelope and spaced from said anode member in a direction toward the other end of said envelope, to cause generation of X-rays directedpaway from said anode member toward said Window member; and means for rotating said envelope to cause said anode member to rotate through said position.

6. An X-ray generating device which comprises: an evacuated envelope; a rotatable anode member defining a portion of said envelope and provided with an internal target surface portion of extended area removed from the axis of rotation of said anode member and movable therewith in a fixed annular path; cathode'means disposed within said envelope and positioned to generate and direct a stream of electrons non-ax'ially from a position at one side of said fixed annular path toward and against said target surface portion at a position on said path' substantially fixed in space, to cause generation of -X-rays directed' away from said target surface portion at the other side of said path; and means for rotating said anode member tocause said target surface portion to pass through said position.

'7. An X-ray generating device which comprises: an elongated-evacuated envelope mounted for rotation about a line extending along the length thereof, and provided with an X-ray-` permeable window member at one end; a conical anode member rotatable with and forming a part of said envelope, symmetrically disposed with respect to: said line at one end of said envelope' and located inwardly of said window member' ad'- jacent said one end; cathode means disposed within said envelope and positioned to direct a stream of electrons toward said one end into im-` pingement upon said conical anode, at a position substantially fixed in space, from a point spaced from said anode member in a'direction" toward the other end of said envelope and non axial with respect to the axis of rotation of said anode member, to cause generation of X-rays directed away from said anode member toward said window member; and means for rotating said envelope to cause said anode member to rotate through said position.

8. An X-ray generating device which comprises: an elongated evacuated envelope mounted for rotation about a line extending lo'ngitudinally thereof, and provided with an annular target surface portion and X-'ray-permeable window means adjacent one end thereof, and including means for generating and directing an electron beam toward said one end into impingement upon said target surface portion to 'cause gen-` eration of X-rays directed from said target portion toward said one end and through said window member; .an-elongated housing member having an open end and adapted to receive said envelope; removable cover member for-said` hous-' ing mounted at the open end thereof; supporting means secured to said cover member and extending inwardly of said housing member, said supporting means being provided with bearing means carrying said elongated envelope, and said housing member and said removable cover member serving to define a container surrounding said envelope and adapted to hold a body of cooling fluid in contact with said envelope; and means for rotating said envelope.

9. An X-ray generating device which comprises: an elongated evacuated envelope mounted for rotation about a line extending along the length thereoi, and provided with an X-raypermeable window member at one end; a conical anode member rotatable with and forming a part of said envelope, symmetrically disposed with respect to said line at one end of said envelope and located inwardly of said Window member adja-' cent said one end; cathode means disposed within said envelope and positioned to direct a stream of electrons toward said one end, along a line substantially parallel to the axis of rotation of said conical anode member and radially spaced from said axis, into impingement upon said conical anode at a position substantially fixed' in space, 'from a point spaced from said anode member in a direction toward the other end of said envelope, to cause generation of X-rays directed away from said anode member toward said window member; and means' for rotating said envelope to cause said anode member to rotate through said position.

10. An X-ray generating device which comprises: an evacuated envelope; a rotatable anode member defining a portion of said' envelope and provided with an internal target surface portion of extended area removed from the axis of rotation of said'anode member and movable therewith in a fixed annular path; cathode means disposed within said envelope and positioned to direct a stream of electrons, from a point at one side of said fixed annular path, along a line substantially parallel to the axis of rotation of said anode member and radiaiiy spaced from said axis into impingement upon said target surface portion at a position on said path substantially fixed in space, to cause generation of X-rays directed away from said target surface portion at the other side of said path; and means for rotating said anode member to cause said target surface portion to pass through said position.

11. An X-ray generating device which comprises: an evacuated envelope; a rotatable anode member defining a portion of said envelope and provided with an internal target surface portion of extended area removed from the axis of rotation of said anode member and movable therewith in a fixed annular path; cathode means disposed within said envelope and rotatable therewith about an aXis extending non-axially with respect to said first-named axis, said cathode means being positioned to direct a stream of electrons non-axially with respect to said firstnamed axis, from one side of said fixed annular path against said target surface portion at a position on said path substantialiy fixed in space, to cause generation of X-rays directed away from said target surface portion at the other side of said path; and means for rotating said envelope and said anode member to cause said target surface portion to pass through said position, said envelope being provided with a fiexibie side-wall portion intermediate the ends thereof and adapted to fiex during rotation whereby the respective axes of rotation of the anode member and cathode means persist in their respective positions during such rotation.

12. The X-ray generating device set forth in claim 11, and comprising in addition an external housing surrounding said evacuated envelope and adapted to contain a body of cooling fluid in contact therewith.

13. An X-ray generating device which comprses: an evacuated envelope; a rotatable anode,

member defining a portion of said envelope and provided with an internal target surface portion of extended area removed from the axis of rotation of said anode member and movable therewith in a fixed annular path; a cathode assembly mounted for rotation about an axis inclined to the axis of rotation of said anode member and having electron emitting means positioned to direct a stream of electrons along the axis of rotation of said cathode assembly from one side of said fixed annular path toward and against said target surface portion at a position on said path substantially fixed in space, to cause generation of X-rays directed away from said target surface portion at the other side of said path; a fiexible tube member hermetically sealed to said anode member and to said cathode assembly, and coopconical anode member rotatable with and forming a part of said envelope, said anode member being provided with an internal target surface portion symmetrically disposed with respect to said line at one end of said envelope and located inwardly of said window member adjacent said one end; cathode means disposed within said envelope and positioned to direct a stream of electrons along a line substantially parailel to but.

.member torotate through said position of impingement 15. An* X-ray generating device which comprises: an elongated evacuated envelope mounted for rotation about a line extending along the length thereof, and provided with an X-raypermeable window member at one end; a hollow conical anode member rotatable with and forming a part of said envelope, said anode member being provided with an internal target surface portion symmetrically disposed with respect to said line at one end of said envelope and located inwardly of said window member adjacent said one end; cathode means disposed within said envelope and positioned to direct a stream of electrons toward said one end from a point spaced from said anode member in a direction toward the other end of said envelope; magnet means located exteriorly of said envelope and positioned to estabiish a magnetic field extending through saidstream of electrons to deect said stream into impingement upon said target surface portion at a position substantially fixed in space, to cause generation of X-rays directed away from said target surface portion toward said window member; and means for rotating said envelope to cause said target surface portion of said anode member to rotate through said position of impingement.

16. An X-ray generating device which comprises: a housing member; an elongated evacuated envelope mounted for rotation within said housing member about a line extending along the length of said envelope, and provided with an X-ray-permeable window member extending transversely across one end thereof, and X-ray producing means disposed interiorly thereof to cause generation of X-rays directed through said window member; bearing means for said envelope, mounted within said housing ext'eriorly of said envelope; a body of lubricating fluid of high dieiectric strength within said housing member and surrounding said envelope and said bearing means; and means for rotating said envelope.

17. An X-ray generating device which comprises: an elongated evacuated envelope; a rotatable anode member defining a portion of said envelope disposed adjacent one end thereof and provided with an internal target surface portion of extended area removed from the axis of rotation of said anode member and movable therewith in a fixed annular path; a cathode assembly located within said envelope and rotatable therewith about an axis which is non-axial with respect to said rotatable anode member and said cathode assembly being provided with electronemtting means located at a'position spaced from said fixed annular path at the side thereof to- Wards the other end of said envelope, said electron-emitting means being positioned to direct an electron stream of small cross-sectonal area from said position toward and against said target surface portion at a. position on said fixed annular path removed from the axis of rotation of said anode member; a flexible tube member her metically sealed to said anode member and to said cathode assembly, and cooperating there- With to define said envelope; and means for rotatng said envelope and said anode member and cathode assembly While mantainng the respective axes thereof relativeiy fixed.

J ESSE W. M. DU MOND. 

